Common endocrine system adverse events associated with immune checkpoint inhibitors

Immune checkpoint inhibitors (ICIs), a novel anti-tumor therapeutic modality, are monoclonal antibodies targeting certain immune checkpoints (ICs) that reactivate T cells to achieve anti-tumor immunity by targeting, binding, and blocking ICs. Targeted inhibitory antibodies against the ICs cytotoxic T-lymphocyte antigen and programmed death receptor-1 have demonstrated efficacy and durable anti-tumor activity in patients with cancer. ICs may prevent autoimmune reactions. However, ICIs may disrupt ICs properties and trigger autoimmune-related adverse reactions involving various organ systems including the cardiovascular, pulmonary, gastrointestinal, renal, musculoskeletal, dermal, and endocrine systems. Approximately 10% of patients with damage to target organs such as the thyroid, pituitary, pancreas, and adrenal glands develop endocrine system immune-related adverse events (irAEs) such as thyroid dysfunction, pituitary gland inflammation, diabetes mellitus, and primary adrenal insufficiency. However, the symptoms of immunotherapy-associated endocrine system irAEs may be nonspecific and similar to those of other treatment-related adverse reactions, and failure to recognize them early may lead to death. Timely detection and treatment of immunotherapy-associated endocrine irAEs is essential to improve the efficacy of immunotherapy, prognosis, and the quality of life of patients. This study aimed to review the mechanisms by which ICIs cause endocrine irAEs providing guidance for the development of appropriate management protocols. Here, we discuss (1) the biological mechanisms of ICs in tumorigenesis and progression, focusing on cytotoxic T-lymphocyte antigen and programmed cell death-1/programmed cell death-ligand 1; and (2) the epidemiology, clinical symptoms, diagnosis, and treatment of four immunotherapy-related endocrine complications.